I haven't seen an official download for that song. It might be coming as is often the case with HSP's songs, although as this is a bootleg remix of someone else's song I'm not sure if he would run into copyright issues by doing that without the original artist's consent. The only ways the get the song at the moment are probably either to use NicoSound (I believe the download button is the one below the graph that says MP3) to rip the original video on Nico Nico Douga, which should yield the best quality, or to use one of the many YouTube converters available to convert one of the reprints on YouTube. Both methods are of course something one decides to use at their own discretion.

Edit

I'll drop you a PM if I notice the track becomes officially available for download.

Edit 2

I can't stop listening to this new song ATOLS just uploaded. I hope he puts it up on iTunes Store like he did with EYE.